<!DOCTYPE HTML>
<html>
    <head>
        <title>Example</title>
        <style>
            canvas {border: thin solid black; margin: 4px}
        </style>
    </head>
    <body>
        <canvas id="canvas" width="500" height="140">
            Your browser doesn't support the <code>canvas</code> element
        </canvas>
        <script>
            var ctx = document.getElementById("canvas").getContext("2d");
            ctx.lineWidth = 20;
            
            ctx.lineJoin = "round";
            ctx.strokeRect(20, 20, 100, 100);

            ctx.lineJoin = "bevel";
            ctx.strokeRect(160, 20, 100, 100);
            
            ctx.lineJoin = "miter";
            ctx.strokeRect(300, 20, 100, 100);
        </script>
    </body>
</html>
